1. Field of Invention
This invention relates to hand trucks commonly called dual hand trucks which can be used in two configurations--the conventional two-wheel configuration and the second configuration as a four-wheel platform truck with castered wheels on one end. Frequently users of hand trucks require alternate uses of the same truck which prompted the design of dual hand trucks at some time in the mid twentieth century. A conventional hand truck utilizes a toe plate on the bottom end of the truck and a pair of handles at the upper end for lifting and transporting a load by levering the toe plate under the load through manual use of handles and transporting the load balanced on the axle of the supporting wheels. Dual truck usage provides a horizontal load-carrying platform with four wheels, one at each corner, as a conventional platform truck is used.
2. Description of Prior Art
Hand trucks of varying designs have been around for the better part of the twentieth century as exemplified in applicants Catalog #190 published in January 1990. The design of hand trucks has varied over the years depending upon a variety of factors such as load capacity and specialized use, as shown in the above-mentioned Catalog. Dual truck designs of the prior art are exemplified in applicant's above-mentioned Catalog on page 12 where a design is shown where two removal pins lock the handle bar from both rotational and sliding movement of the handle bar in a DT series design. Another design is shown on page 12 of the same Catalog which is the EDT series wherein two pins lock the handle bar in one of a pair of fixed sleeves which are positioned 90.degree. from each other. Another prior art design is shown on page 16 of said catalog which is an ADT series design which pivotally latches the lower ends of handle bar legs both to the side rails of the truck and also against any rotational movement of the handle bar relative to the side rails. This latter design compared to the present invention does not have the functional reliability of the design of the present invention and is subject to malfunction under heavy use.